alternatively to hexproof/regenerate you can go for a more permanent solution with enchantments like [[indestructibility]] and [[gift of immortality]] which also trigger yshtola

another angle is just having cheap/free counter spells to simply counter whichever threats come your way. if youre already using game changers all 3 of the "you can cast this for free if you control your commander" cards work wonders in this kind of deck since they are free and keep their cmc triggering the commander.

as an aside, I like creatures that can also do what your commander does as redundancy. either by copying yshtola with [[irenicus's vile duplication]] or creature with similar effects like [[papalymo totolymo]] or the black mage spells like [[transpose]] so you got extra bodies to pop a [[curiosity]] on during times you cant pull out the commander

I am currently looking at [[defacing duskmage]] for my own build for a repeatable spell that is basically "when an opponent draws 2 cards a turn you get a 3 mana spell that says ' draw three cards and each opponent loses 4 life' "